Trench MOSFET having gate electrode over shielded electrode structure provides advantages over conventional trench MOSFET, such as reduced gate to drain charge Qgd, and reduced on-resistance. See for example, U.S. Pat. Nos. 5,998,833 and 7,768,064. The superior performance of the trench MOSFET having shielded electrode is an excellent choice for DC/DC converter. Meanwhile, in order to further increase the efficiency of the trench MOSFET having shielded electrode, the parasitic PN body diode of the trench MOSFET must be prevented from turning on, because once the parasitic PN body diode is turned on, both electron and hole carriers are generated that requires longer time to eliminate these carriers through the electron-hole combinations, thus reducing the efficiency of the trench MOSFET. Therefore, a Schottky rectifier is chosen to be implemented as a clamping diode in parallel to the parasitic PN body diode to prevent the body diode from turning on because that, the Schottky rectifier is operated with a single carrier, e.g., the carriers consisted of electrons only, and this single type of carriers can be drawn from the drain electrode. Therefore, the Schottky rectifier is an effective and preferred clamping diode to increase the operational efficiency of the semiconductor power device. The Schottky clamping operation can be realized when the forward voltage Vf of the Schottky rectifier is less than the parasitic diode that is approximately 0.7 volts.
Accordingly, it would be desirable to provide a new and improved device configuration to further improving the characteristic of the trench MOSFET having shielded electrode by integrating a trench Schottky rectifier on a single chip.